1. Field of the Invention
The present invention relates to portable terminal that uses a battery as a power supply and to a method for controlling peripheral circuits in portable terminal.
2. Description of Related Art
In this type of portable data terminal such as disclosed, for example, in Japanese Unexamined Patent Publication(KOKAI) No. 61-86877, when the power supply voltage drops or when a power supply is connected having a voltage that has dropped, faulty operation by stored data or a program is prevented by preventing the start of operation, and stored of data or a program is protected from being destroyed.
FIG. 8 shows an example of the configuration of this type of prior art.
In this drawing, reference numeral 85 denotes a power supply voltage detection means, this being connected to a controller 86 and a starting signal control means 87, and 88 is a starting signal outputting means, which is connected to the starting signal control means 87. The starting signal control means 87 is connected to the controller 86. While the reference numeral 89 denotes a memory section, which is connected to the controller 86.
The operation of the above-noted example will now be described.
In the configuration of FIG. 8, when the power supply voltage drops, the power supply voltage detection means 85 outputs a detection signal 81 to the controller 86 and to the starting signal control means 87.
When this detection signal changes to the high level, the controller 86 judges that the power supply voltage has dropped, and notifies the operator of this event. The controller 86 also stops operation.
When the detection signal changes to the high level, that is, when the power supply voltage drops or a power supply is connected that has a voltage that has dropped, if there is an input from the operator to start operation, a start signal (low level) is output from the start signal outputting means 88 to the start signal control means 87.
When this happens, because the detection signal is input from the power supply voltage detection means 85, the start signal control means 87 does not output a start signal 83 to the controller 86.
When the power supply voltage is normal (when it reaches the reference voltage), and when there is an input from the operator to start operation, the start signal 83 is output from the start signal outputting means 88 to the controller 86, via the start signal control means 87.
This start signal control is shown in FIG. 9.
FIG. 9(A) shows the start signal control in the case in which the power supply voltage drops or in which a power supply is connected which voltage has dropped, while FIG. 9(B) shows the starting signal control in the case in which the power supply voltage is normal.
In the prior art, because the starting signal control depends upon whether or not the power supply voltage is a voltage at which normal operation is possible, when the power supply voltage drops or when a power supply is connected which voltage has dropped, even if the operator makes an input to start operation the terminal will not occur, offering the advantage of protecting stored data and programs.
The configuration of the power supply lines in the past is shown in FIG. 10.
The configuration shown in FIG. 10 is formed by a power supply 101 which is indicated as a battery, a voltage raising means, such as a booster or the like, 102 for the purpose of boosting the voltage so as to supply a constant voltage, a control means 103 which controls the switching means 104 and 105, switching means 104 performing on/off switching of the supply of power to a peripheral circuit 106, and switching means 105 performing on/off switching of the supply of power to a peripheral circuit 107, and peripheral circuit 106 and peripheral circuit 107 starting and operating only when they are supplied with electrical power.
In a portable terminal such as a terminal that is carried about, a battery is usually used as the power supply.
Because a battery is not capable of supplying a stabilized voltage to at all times with a varying supply current, a voltage raising means 102 is used to stabilize the supplied voltage.
For this reason, while the voltage on the power supply line A varies, there is almost no variation on the power supply line B.
In a portable terminal, to extend the limited life of a battery as much as possible, the supply of power to a circuit that is not being used is stopped.
The control means 103 judges whether or not the peripheral circuits 106 and 107 are being used and, if they are not being used, stops power supply thereto by means of the switching means 104 and 105.
Because on/off control of the power supply to the peripheral circuits 106 and 107 must be performed by the control means 103, it must always be supplied with power, via power supply line B.
FIG. 11 shows the transitions of voltage supply conditions on the power supply lines shown in the above-noted power line configuration drawing, the transition of the voltages after the switching means, these being the transition of the supply condition of the voltages C and D as shown in FIG. 10, occurring before transition of the voltage after the voltage boosting means, which is the transition of the voltage B as shown in FIG. 10.
In this drawing, the horizontal axis represents time, and this drawing represents the passage of time from a to d.
In terms of the example of the switching of the voltage supplied to the peripheral circuit 106, at time a the supply of electrical power to the peripheral circuit 106 begins.
At this point, because there is a sudden flow of current into the peripheral circuit 106, there is a drop in the voltage on the power supply line C.
In a circuit having a storage means such as a capacitor, because the capacitor begins storage when the supply of power thereto is started, this causes a sudden flow of current.
For this reason, the voltage drops temporarily. This voltage drop passes through the switching means 104 and propagates to the voltage raising means 102, so that a delay occurs, after which the voltage on power supply line B drops.
This drop in voltage is detected, and the voltage boosting means 102 increases the amount of current supplied, thereby stabilizing the voltage.
At time c, the power supply line B is stable. Because of this stabilized power supply line B, the power supply line C is also stabilized.
However, because there is propagation via the switching means 104, a delay will be continued until the time d occurs.
Also, in the case in which a circuit is started which suddenly consumes a large amount of power, the same type of phenomenon as described above occurs, independent of the start of application of power.
Thus, when starting to supply power to a circuit, and when starting circuit with a large power consumption, a temporary voltage drop occurs.
On the other hand, the Japanese Unexamined Patent Publication (KOKAI) No. 1-95065 shows a portable terminal device by which the power consumption of a battery will be reduced.
More over, the Japanese Unexamined Patent Publication (KOKAI) No. 4-160415 also shows a portable terminal having a control circuit by which the power consumption of a battery will be reduced.
However, in these conventional technologies, a specific circuit so as to reduce the power consumption of the battery is introduced into these portable circuit but these documents fail to show or suggest the technical conception that the remaining voltage capacitance is used for controlling to execute a plurality of peripheral circuits, taking each of sufficient power voltage by which the respective peripheral circuit can work normally, into the account.
A first problem occurring in the prior art is that, even in the case in which the amount of remaining battery capacity is insufficient at times other than start-up, the operation of a circuit which consumes a large amount of power causes a drop in voltage, this leading to the possibility of faulty operation.
The reason for this is that, although the battery itself might have insufficient capacity, it might be capable of causing operation of a circuit with low power consumption. When the supply of current to a circuit is started, because of the temporary flow of a large amount of current, there is a temporary drop in the voltage supplied to the circuit.
A second problem occurring in the prior art is that, although a circuit might itself have a low power consumption, if supply is started to a number of such circuits simultaneously, or if a number of these circuits are started simultaneously, the voltage can drop, leading to the possibility of faulty operation.
The reason for this is that, when using one application, there are cases in which a number of peripheral circuits should be used.
In such cases, when using an application, it can begin to start the supply of power to a number of peripheral circuits simultaneously.
A third problem occurring in the prior art is that, because of the large power consumption of the voltage detection circuit, in a portable terminal which uses a battery as a power supply, the power consumption there of is excessively large.
The reason for this is that, to enable accurate voltage detection in the voltage detection means, an A-D (analog-digital) converter is required. The A-D converter requires a sampling clock, and the oscillation of this clock consumes electrical power.
A fourth problem is that, in the case of a mere temporary restoration of the battery voltage, there is a possibility that startup and faulty operation will occur.
The reason for this is that if a battery with little remaining capacity is used without a load or with a small load, there is a temporary restoration to a supply of the normal voltage.
An object of the present invention, is to prevent faulty operation in a portable terminal in which the power supply voltage has dropped, and to prevent the destruction of data and a program by such faulty operation.
Another object of the present invention is, in the case in which the above-noted faulty operation occurs, to prevent the terminal from being left in this faulty operating condition, and to prevent the backup battery of the terminal to be consumed in this faulty operating condition, thereby preventing the total loss of a stored program or data.
Yet another object of the present invention is, in the case of the startup of the terminal when the operator is not present, to prevent the above-noted faulty operation, and to prevent the consumption of even the backup battery of the terminal without applying any form of countermeasure, thereby preventing the total loss of a stored program or data.